This invention relates generally to a supercharger, and more particularly to a control apparatus to control air flow through a supercharger compressor.
In one present supercharger system utilizing a blower, the air from the blower discharge is connected back to the inlet of the blower through a valve. When the valve is shut, the blower supercharges the engine. When the valve is open, the blower recirculates air without generating pressure. This is especially applicable to blower systems where there is no built in compression ratio, as compared to compressor supercharger systems where there is built in compression ratio in the compressor itself.
A compressor with a built in compression ratio will draw air into the working chamber, then compress the air by reduction of volume of the working chamber before the compressed air is brought to the discharge opening. Compressors without a built in compression ratio draw air into a working chamber, then open the working chamber to the discharge opening, resulting in high pressure air flowing through the discharge opening in the reverse direction compressing the air in the working chamber. Compressors with built in compression ratios are generally more efficient.
A Roots blower is an example of a compressor without a built in ratio. A twin screw compressor is an example of a compressor with a built in ratio. It is well known that plug valves used in twin screw compressors will relieve the pressure in the working chamber during unloaded operation, which reduces compressor power. These valves generally are actuated by the compressor discharge pressure which is above atmospheric pressure.
In a supercharger application, however, compressor discharge pressure alternates between above and below atmospheric pressure. Therefore, a way to control the supercharger under various engine demands must be found.
The foregoing illustrates limitations known to exist in present supercharger systems. Thus, it is apparent that it would be advantageous to provide an alternative directed to overcoming one or more of the limitations set forth above. Accordingly, a suitable alternative is provided including features more fully disclosed hereinafter.